CVE-2021-39899

Account compromise via IP-sharded password brute force

Published Oct 4, 2021 · Updated Aug 4, 2024

Improper rate limiting in GitLab before 14.1.7, 14.2.5, and 14.3.1 allows physically proximate attackers to brute-force passwords. The change-password function accepts a stolen session across source addresses, allowing its per-IP request limit to be divided among multiple IP addresses. Physical access to a signed-in user's machine is required to obtain the session; a successful guess exposes the password and enables account takeover.

CVSS severity4.2
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper rate limiting in GitLab before 14.1.7, 14.2.5, and 14.3.1 allows physically proximate attackers to brute-force passwords. The change-password function accepts a stolen session across source addresses, allowing its per-IP request limit to be divided among multiple IP addresses. Physical access to a signed-in user's machine is required to obtain the session; a successful guess exposes the password and enables account takeover.

The record

CVE
CVE-2021-39899
Published
Oct 4, 2021
Updated
Aug 4, 2024
Vendor
GitLab
Product
GitLab
Classifications
CWE-640, T1110.001
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>=1.0, <14.1.7
  2. Affected versionversion=>=14.2, <14.2.5
  3. Affected versionversion=>=14.3, <14.3.1

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

GitLab · GitLabversion=>=1.0, <14.1.7; version=>=14.2, <14.2.5; version=>=14.3, <14.3.1

Published CVSS scores

1.9NIST NVDAV:L/AC:M/Au:N/C:P/I:N/A:N
2.9GitLab Inc.CVSS:3.1/AV:P/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
4.2NIST NVDCVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-640Weak Password Recovery Mechanism for Forgotten Password
T1110.001Brute Force: Password Guessing

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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